Study on the powder mixing and semi-solid extrusion forming process of SiCp/2024Al composites

doi:10.1016/S0924-0136(01)00738-5

Journal of Materials Processing Technology

Volume 114, Issue 3, 7 August 2001, Pages 189-193

https://doi.org/10.1016/S0924-0136(01)00738-5 Get rights and content

Abstract

In this paper, the powder mixing and semi-solid extrusion technology for fabricating SiCp/2024Al composites and the material’s microstructure feature and mechanical properties were studied. From the extrusion stress–displacement curves of semi-solid extrusion under different temperature, it is found that the deformation force during semi-solid extrusion is low and steady. The microstructure of SiCp/2024Al composites fabricated by the present method is characterized by a well-densified matrix and uniformly distributed reinforcement particles, and there is no apparent interface reaction. Compared to matrix alloys, the elastic modulus, yield strength and ultimate tensile strength of SiCp/2024Al composites have been substantially improved. Compared to similar composites fabricated by other technologies, SiCp/2024Al composites fabricated by the present technology in this paper possess relatively higher elongation.

Introduction

The importance of particulate reinforced metal matrix composites (PMMCs) due to high specific strength, high specific modulus, better resistance to wear and thermal steadiness has attracted much interest in the development of the manufacturing process for such composites. The forming processes of PMMCs are mainly conventional casting, stirring casting in the semi-solid state and powder metallurgy technology. Casting techniques are very promising for manufacturing composites parts at relative low cost. However, in casting methods, reactants often appear at the interface between the matrix and the reinforcement, which deleteriously affects the mechanical properties of the final composites [1], [2]. The technology of powder metallurgy can improve the mechanical properties of the materials, but at the same time they increase the production cost because of the complex working procedure [3]. Considering the above, a semi-solid extrusion technology based on the powder method to fabricate SiCp/2024Al composites has been put forward in this paper for the first time.

The technology of powder mixing is employed to uniformly mix SiC powder and 2024Al powder. The volume fraction of SiC particles can be freely modified. Forming in the semi-solid state offers the advantages, on the one hand compared with the liquid state, of avoiding the extensive reaction that can occur between the molten metal and the reinforcements and, on the other hand, of an excellent deformability under very low flow stresses relative to those for the fully solid state [4], [5], [6]. Moreover, the cracking of SiC particles and the decohesion of the interface between the SiC particles and the matrix can be avoided during semi-solid forming, which are of benefit to the mechanical properties of the final composites.

In this paper, the powder mixing and semi-solid extrusion technology for fabricating SiCp/2024Al composites is discussed.

Section snippets

Experimental materials and procedure

The powder of 2024Al alloy used in this experiment was prepared by argon supersonic atomization, its chemical composition being Al–4.48 wt.%Cu–1.45 wt.%Mg–0.61 wt.%Mn–0.31 wt.%Fe–0.15 wt.%Si. The powder of size 7 μm was supplied by the grinding wheel factory in Mu Danjiang, China. The volume fraction of SiCp is 20%. The processing flowchart of the fabrication of the SiCp/2024Al composites with the powder mixing and the semi-solid extrusion is shown in Fig. 1, the specific procedure and processing

Deformation force

The extrusion stress–displacement curve was a characteristic curve for describing semi-solid extrusion. Fig. 2, Fig. 3 show the extrusion stress–displacement curves under different temperatures and of the different powder performs under the extrusion ratio of 10:1. From Fig. 2, Fig. 3, it can be seen that the process of semi-solid extrusion comprises two stages: (1) the extrusion stress rapidly increases with the lowering of the punch, and reaches the peak value, subsequently, the process of

Conclusions

The powder mixing and semi-solid extrusion technology for fabricating SiCp/2024Al composites, and the material’s microstructure and mechanical properties were investigated, from which the following results could be drawn:

1.
The powder mixing and semi-solid extrusion process can fabricate sound composite bars. SiC particles are uniformly distributed in the matrix, and there is no decohesion of the interface between SiC particles and 2024Al.
2.
The deformation force of semi-solid extrusion is only $15 – 13$

Acknowledgements

This study was financially supported by the National Natural Science Foundation of China under contract No. 59675050.

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Study on the powder mixing and semi-solid extrusion forming process of SiCp/2024Al composites

Abstract

Introduction

Section snippets

Experimental materials and procedure

Deformation force

Conclusions

Acknowledgements

J. Mater. Proc. Technol.

Acta Metall.

Int. J. Plast.

Acta Metall. Mater.